Chillers of the type defined above must be purged of non-condensables which tend to accumulate in the condenser section of the chiller. Such non-condensables are detrimental to the performance and efficiency of such chillers and even small quantities have a pronounced deleterious effect. Such non-condensables are generally purged via a purge line leading to the evaporator section of the chiller. Through such purge line water vapor is blown with entrained non-condensables. As the non-condensables constitute only a small portion of the vapor blown to the evaporator, such vapor constitutes a loss to the system and such losses ought to be minimized. This is of special importance with devices based on the use of solar energy where losses ought to be minimal.